1. Field
The present invention concerns a centrifugal deflection device intended to be fitted to a surgical or dental handpiece for removing the foreign matter that results from an operation. More specifically, this invention concerns a device of this type that includes a ring preventing foreign matter that results from an operation from penetrating the handpiece to which the ring is fitted.
2. Related Art
An operation such as the removal of a wisdom tooth inevitably produces debris such as bone or tooth fragments, blood or secretions of saliva. It is imperative that this debris is removed to leave the operating field clean so that the practitioner can clearly see the work he is carrying out. The debris must also be prevented from penetrating the handpiece because it is liable both to damage and to contaminate the instrument.
A device for preventing foreign matter from penetrating the rear zone of a dental handpiece is known from EP Patent Application No. 0 471 916 A1. This handpiece includes a body, a gripper section and a nose section. The nose section includes a main member and a cap, detachably mounted for example by screws, to the main member of the nose section. The cap is provided with four radial, equiangularly spaced evacuation apertures. A sleeve for receiving and securing a dental tool in cooperation with a drive shaft is radially mounted on the foremost end of the drive shaft. An end cap forming an additional rotating member is screwed onto the outer periphery of the sleeve. The end cap has an inner flange in contact with the dental tool and an outer flange extending radially outwardly. An annular chamber communicating at one end with an opening for inserting a dental tool and at the other end with the front face of a bearing located in the rear area of the instrument is delimited between the outer periphery of the end cap and the nose cap.
The device for preventing foreign matter from penetrating the handpiece briefly described above operates as follows. When the drive shaft is rotating, the sleeve and the end cap rotate together, which induces a flow of air around these elements. Given that the radius of rotation of the end cap is larger than that of the sleeve, the circumferential velocity of the end cap is higher than that of the sleeve. Above all, the radius of rotation of the outer flange is the largest and hence the air flow velocity around the outer periphery of the outer flange is the highest so that the air pressure around the outer flange is lower in proximity to the foremost part of the handpiece. A pressure gradient is thus created, which decreases progressively from the dental tool insertion opening towards the inside of the handpiece. During the operation, foreign matter such as debris from the tooth being treated penetrates the handpiece through the dental tool insertion opening and is sucked up by the pressure gradient effect into the inside of the handpiece. This debris moves around in the annular chamber in which the pressure is lower until it reaches the outer flange where the pressure is the lowest. The debris is then expelled towards the exterior through the evacuation apertures by the centrifugal force effect of the end cap. Thus, foreign matter is prevented from penetrating the rear area of the instrument.
It is clear that, in the case of the device disclosed in the aforementioned EP Patent Application No. 0 471 916 A1, the air flow pressure decreases the more the air flow penetrates the handpiece. It therefore seems, from the foregoing, that the front face of the bearing located in the rear area of the handpiece is suitably protected by the outer flange of the end cap, which deflects foreign matter towards the evacuation apertures and forms an obstacle preventing the foreign matter from moving forward towards the front face of the bearing. However, the device described above does not totally prevent debris from penetrating the handpiece. Indeed, debris penetrates the handpiece through the dental tool insertion opening and moves around inside the annular chamber delimited between the nose cap and the outer periphery of the end cap. The debris thus inevitably dirties these elements and may even reach the drive shaft and alter the working of the handpiece. Consequently, between two successive patients, the entire nose section has to be dismantled from the handpiece, namely the nose cap, the end cap and the sleeve so that these elements can be cleaned and the handpiece completely sterilised, which is difficult and time consuming.